Internal combustion engines combust an air and fuel mixture within cylinders to reciprocally drive pistons within the cylinders. The pistons rotatably drive a crankshaft to provide drive torque to a powertrain. Exhaust generated by the combustion process is exhausted from the engine through an exhaust manifold, is treated in an exhaust system and is released to atmosphere.
Engine systems often include an exhaust gas recirculation (EGR) system to reduce engine emissions. EGR involves re-circulating exhaust gases back into the cylinders, which limits the amount of oxygen available for combustion and lowers cylinder temperatures. EGR enables ignition timing to remain at an optimum point, which improves fuel economy and/or performance. However, debris build-up within the EGR system restricts exhaust flow therethrough and minimizes the effectiveness of the EGR system.
A traditional method of monitoring the flow restriction through the EGR system is to determine a peak manifold absolute pressure (MAP) difference between MAP levels when the EGR is ON and when the EGR is OFF. This method provides distinct disadvantages in that the MAP difference can have high variation under different engine operating conditions and it is difficult to calibrate compensation factors for the various engine operating conditions. Further, the MAP difference can be contributed to other factors that are independent of the EGR system.